At the present time reading and writing in optical disk memory systems requires the critical adjustment and control of components and operational conditions due to environmental tolerances that affect the read/write head. Currently read/write optical heads are relatively expensive and have a higher than desirable mass because they carry the laser diodes that are used for reading and writing. In addition, the implementation of Direct Read After Write (DRAW) is highly desirable but it is costly to implement because of the construction of present day optical read/write heads.
The present invention, by mounting the laser diode on a stationary temperature controlled platform, and by using a polarizing-preserving single mode fiber to make a flexible link between the laser and the optical head, provides a read/write head of approximately one-sixteenth the size and mass of conventional read/write heads, relaxed alignment tolerances and extended temperature ranges of operation. By inserting a magnifying lens at the input to the optical fiber the general elliptically shaped beam that is emitted by the laser diode is converted to a generally circularly shaped beam by placing a collimating lens on the output end of the optical fiber. The elliptical output beam from the laser diode can be substantially matched in size to the effective circular aperture on the input end of the fiber after magnification by the magnifying lens.
The magnifying lens, the laser diode and the polarizing-preserving single mode optical fiber, therefore, all function as a spatial filter which eliminates the problems that are caused by laser diodes which have large astigmatic distances. The use of low cost diodes and the improved feasibility of using closed loop power control are additional features of the present invention.